The Nuclear Magnetic Resonance (NMR) phenomenon was discovered in 1946 and soon afterwards applied in the fields of physics, chemistry, materials science, life sciences, and medicine. In the 1950s, nuclear magnetic resonance began to be used in the oil and gas industry, initially in the field of reservoir rock physics. The NMR logging tool can use the principle of nuclear magnetic resonance to detect the stratum information around the wellbore, and has unique qualitative identification and quantitative evaluation capabilities on a reservoir fluid.
A probe is one of the important components of the nuclear magnetic resonance logging tool. The structure of the probe determines the key performance such as measurement method of the tool, nuclear magnetic resonance region and nuclear magnetic resonance signal strength. The probe for the nuclear magnetic resonance logging tool mainly includes a magnet and an antenna. The magnet can form a static magnetic field for polarizing a spin hydrogen proton, and the antenna can transmit an radio frequency field for turning the spin hydrogen proton, and after removing the radio frequency field, the spin hydrogen proton begin to process along the static magnetic field, which produces a nuclear magnetic resonance inductive signal, the stratum conditions can be analyzed by detecting the nuclear magnetic resonance inductive signal.
The probe in existing nuclear magnetic resonance logging tool mostly uses a columnar magnet. The two ends of the magnet are N pole and S pole respectively. The magnetic field distribution is formed by closed magnetic lines from the N pole pointing to the S pole. The antenna surrounds the magnet and can excite the polarized stratum region at 360° around the wellbore so that there is no detection blind region around the wellbore and it is possible to perform multi-frequency and multi-slice measurement, but the measured signal can only be an average signal of signals in the stratum at 360°. Therefore, the nuclear magnetic resonance logging tool in the prior art can only perform signal detections of radial depth dimension and axial depth dimension, and does not have signal detection capability of circumferential multi-directional sensitive region, and further, there is no driving device that can drive the nuclear magnetic resonance logging tool to perform three-dimensional scanning.